Currently, units engage in melee combat when a unit is in base-to-base contact with another unit & melee attacks are dealt. This means you can be in base-to-base contact or move into base-to-base contact with another unit & not automatically attack or be attacked. 

Most games do not let you go into base-to-base contact without charging & following that with an attack.

The idea here is to remove the sometimes awkward 1 inch checks when moving a unit. I've not found any other systems similar in this regard (maybe for good reason.)

I, myself, am enjoying it this way so please share your thoughts on the system